Oversampling pulse oximeter
First Claim
1. A pulse oximeter, comprising:
- a first source for emitting light having a first spectral content;
a second source for emitting light having a second spectral content different than said first spectral content;
a drive system for pulsing each of said first and second sources such that said first and second sources output first and second optical signals, respectively, each of said first and second optical signals including a series of high output periods separated by low output periods, said drive system thereby defining a multichannel modulation waveform wherein said first and second sources are pulsed in a non-alternating fashion to define a non-alternating multiplexed optical signal;
a detector for receiving said non-alternating multiplexed optical signal and providing a non-alternating multiplexed detector signal representative of said received non-alternating multiplexed optical signal;
a digital sampler, operatively associated with said detector, for providing multiple digital values based on said non-alternating multiplexed detector signal corresponding to a single cycle state, said single cycle state being one of a single high output period and a single low output period of one of said first and second sources; and
a processor for using said multiple digital values in performing processing steps related to determining an oxygen saturation related value.
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Accused Products
Abstract
An oversampling pulse oximeter includes an analog to digital converter with a sampling rate sufficient to take multiple samples per source cycle. In one embodiment, a pulse oximeter (100) includes two mor more light sources (102) driven by light source drives (104) in response to drive signals from a digital signal processing unit (116). The source drives (104) may drive the sources (102) to produce a frequency division multiplex signal. The optical signals transmitted by the light sources (102) are transmitted through a patient'"'"'s appendage (103) and impinge on a detector (106). The detector (106) provides an analog current signal representative of the received optical signals. An amplifier circuit (110) converts the analog current signal to an analog voltage signal in addition to performing a number of other functions. The amplifier circuit (110) outputs an analog voltage signal which is representative of the optical signals from the sources (102). This analog voltage signal is received by a fast A/D converter (112) which samples the analog voltage signal to generate a digital voltage signal which can be processed by the digital signal processing unit (116). The fast A/D converter (112) operates at a rate sufficient to take multiple samples per source cycle and may have a sampling frequency, for example, of over 41 kHz. The digital signal processing unit (116) implements software for averaging the samples over a source cycle for improved measurement consistency, improved signal to noise ratio and reduced A/D converter word length.
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Citations
28 Claims
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1. A pulse oximeter, comprising:
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a first source for emitting light having a first spectral content;
a second source for emitting light having a second spectral content different than said first spectral content;
a drive system for pulsing each of said first and second sources such that said first and second sources output first and second optical signals, respectively, each of said first and second optical signals including a series of high output periods separated by low output periods, said drive system thereby defining a multichannel modulation waveform wherein said first and second sources are pulsed in a non-alternating fashion to define a non-alternating multiplexed optical signal;
a detector for receiving said non-alternating multiplexed optical signal and providing a non-alternating multiplexed detector signal representative of said received non-alternating multiplexed optical signal;
a digital sampler, operatively associated with said detector, for providing multiple digital values based on said non-alternating multiplexed detector signal corresponding to a single cycle state, said single cycle state being one of a single high output period and a single low output period of one of said first and second sources; and
a processor for using said multiple digital values in performing processing steps related to determining an oxygen saturation related value. - View Dependent Claims (2, 3, 4, 5, 6, 7, 8, 9, 10)
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11. A pulse oximeter, comprising:
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a first source for emitting light having a first spectral content;
a second source for emitting light having a second spectral content different than said first spectral content;
a drive system for pulsing each of said first and second sources such that said first and second sources output first and second optical signals, respectively, each of said first and second optical signals including a series of high output periods separated by low output periods, said drive system thereby defining a multichannel modulation waveform wherein said modulation waveform includes at least one overlap time period where said first and second sources are simultaneously in a high output state during said overlap time period;
a detector for receiving said first and second optical signals and providing a detector signal representative of said received first and second optical signals;
a digital sampler, operatively associated with said detector, for providing multiple digital values based on said detector signal corresponding to said overlap time period; and
a processor for using said multiple digital values corresponding to said overlap time period in performing processing steps related to determining an oxygen saturation related value. - View Dependent Claims (12, 13, 14, 15, 16, 17, 18, 19, 20, 21)
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22. A pulse oximeter, comprising:
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a first source for emitting light having a first spectral content;
a second source for emitting light having a second spectral content different than said first spectral content;
a drive system for pulsing each of said first and second sources such that said first and second sources output first and second modulated optical signals, respectively, each of said first and second optical signals including a series of high output periods separated by low output periods;
a detector for receiving said first and second optical signal and providing a detector signal having a detector signal waveform representative of said received first and second optical signals;
a digital sampler, operatively associated with said detector, for providing a series of digital values, each said digital value corresponding to a value of said detector signal relating to a portion of said detector signal waveform having a time component that is substantially shorter than said high output periods of said sources, whereby said series of values includes multiple values corresponding to said high output periods, said series of values defining a digital signal; and
a processor for performing processing steps related to determining an oxygen saturation related value, said processor including logic for monitoring said digital signal to obtain digital signal information and controlling demodulation of said digital signal based on said digital signal information. - View Dependent Claims (23, 24, 25, 26, 27, 28)
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Specification